This application is based on and claims priority under 35 U.S.C. xc2xa7 119 with respect to Japanese Application No. 2000-080468 filed Mar. 22, 2000 and Japanese Application No. 2000-390722 filed Dec. 22, 2000, the entire contents of both applications are incorporated herein by reference.
1. Field of the invention
This invention relates to a sewing machine.
2. Description of related arts
An embroidery sewing machine, as an example of a conventional sewing machine, will be described as follows: An embroidery sewing machine comprises a) a frame holder holding an embroidering frame to restrain the cloth to be embroidered, b) an electric motor transferring the frame holder during embroidering, c) a needle driver for driving a sewing needle, and d) a controller for intelligently regulating the electric motor and the needle driver. Recently, an improved embroidery sewing machine works more accurately. The mass of the cloth, restrained on the embroidering frame, is varied. Furthermore, it is possible to attach a variety of embroidering frames, having different masses, to the sewing machine. Thus the various masses of the cloth and the various masses of the embroidering frame have a large influence on the sewing accuracy of the embroidery sewing machine. If the masses of the cloth and the embroidering frame are large, a fast embroidering speed vibrates the embroidery sewing machine and sags the embroidering frame because of a larger inertia thereof.
Thus improvement in embroidering accuracy of the embroidery sewing machine is limited.
To overcome the above problem, a conventional embroidery sewing machine comprises a setting means enabling selection of either a small mass material embroidering mode or a large mass material embroidering mode. The small mass material embroidering mode is one embroidering mode for cloth having a small mass. The large mass material embroidering mode is the other embroidering mode for cloth having a large mass. A person operating the embroidery sewing machine first decides whether the cloth to be embroidered has a large mass or not, and second inputs either the small mass embroidering mode or the large mass embroidering mode into the setting means for embroidering accuracy. If the cloth to be embroidered has a small mass, then the controller regulates the sewing machine to embroider at a rapid speed depending on the embroidering mode input by the person. If the cloth to be embroidered has a large mass, then the controller regulates the sewing machine to embroider at a slow speed. However, it is impossible for the person to accurately select whether the cloth has a large mass or not based upon eyesight. Both a material of the cloth (i.e. soft or stiff) and a condition for restraining the cloth on the embroidering frame (i.e. the cloth having a freely swingable portion extending off the embroidering frame) influence an inertia of the embroidering frame. Accordingly, if the person confirms the mass of the cloth only by eyesight, and determines whether the cloth is embroidered in the larger mass embroidering mode or the small mass embroidering mode, the selection of embroidering modes is not accurately suitable to the inertia of the embroidering frame, thus limiting any improvement in embroidering accuracy.
Accordingly, it is an object of the present invention to provide an improved sewing machine.
It is another object of the present invention to provide an improved sewing machine which obviates the above conventional drawbacks.
It is a further object of the present invention to provide a sewing machine which can estimate the mass of the material to be sewn. The sewing machine can accurately move the material, thereby providing a suitable sewing condition according to the mass of the material, and thereby obtaining sufficient embroidering accuracy.
In accordance with a first aspect of this invention, a sewing machine comprises a movable holder portion for holding a material to be sewn, a holder drive portion for moving the holder portion during sewing of the material, a needle drive portion for driving a sewing needle to sew, and a controller for regulating the holder drive portion and the needle drive portion. The controller includes an initial motion means for moving the material to be sewn before sewing or in an initial stage of sewing, and an estimating means for estimating a mass of the material depending on a physical value such as a moving speed of the material or a moving distance of the material for a predetermined period of time.
In accordance with a second aspect of this invention, the sewing machine further comprises an estimated mass adaptive control means for automatically adjusting a control mode based on the estimated mass of the material by the estimating means.
In accordance with a third aspect of this invention, the sewing machine determines the physical value based upon a driving speed of an initial movement of the movable holder portion holding the material or a driving distance of the holder drive portion for the predetermined period of time.
Thus, the present invention has the following advantages. In the sewing machine of this invention, before sewing or at the initial stage of sewing, the holder portion holding the material to be sewn is initially moved by the initial motion means. In the initial moving of the holder portion, the estimating means estimates the mass of the material to be sewn depending on the physical value of at least one of the moving velocity of the material and the moving distance of the material. Under the same conditions as the holder portion and the holder drive portion before the initial moving thereof, when the material is moved slowly during the initial moving, the estimating means determines the mass of the material to be large. When the material is moved rapidly during the initial moving, the estimating means determines the mass of the material to be small.
Also, under the same conditions of the holder portion end the holder drive portion before the initial moving thereof, when the moving distance within a predetermined amount of time is small, the estimating means determines the mass of the material to be large. When the moving distance within the predetermined amount of time is large, the estimating means determines the mass of the material to be small. Since mass generally corresponds to weight, the weight of the material is automatically determined based upon the mass of the material.
The sewing machine of this invention can automatically adjust a sewing condition thereof depending on the mass of the material estimated by the estimating means.
Thus accuracy of sewing, such as embroidering, can be kept independently of the mass of the material on the holder portion.
The sewing machine of this invention comprises the estimated mass adoptive control means which automatically determines the optimal control mode for regulating the holder drive portion. The estimated mass adoptive control means determines the optimal control mode depending on the mass of the material estimated by the estimating means. The estimated mass adoptive control means finds the optimal control mode for the holder drive portion and sets a constant for regulating the holder drive portion. The constant is optimally set (for accurately positioning the holder portion within a short response time) due to being precisely analyzed. When the mass of the material is large, the holder drive portion is driven slowly by the control mode set by the estimated mass adoptive control means. When the mass of the material is small, the holder drive portion is driven rapidly.